The emission bands exchibited by films of polyimides derived from 1,3-bis(3,4-dicarboxyphenoxy)benzene dianhydride, hexafluoroisopropylidenedibenzene-3,3`,4,4`-tetracarboxylic dianhydride, and aromatic and heteroaromatic diamines, and also of polyamides and polyquinazolones derived from the same amines are exciplex bahnds. With polyamides, complexes in the ground state are formed. The fluorescence of the photoconductivity sensitizer Rhodamine 6G is quenched in films of these polymers by the exciplex mechanism.Aromatic polyimides [1], polyamides [2], and poorly studied polyquinazolones [3] exhibit high heat resistance, high optical transparency, and good dielectric and film-forming properties; when modified with functional photosensitive fragments, they can be used in development of materials for optical technologies. Photosensitive polymers are of considerable interest from the viewpoint of their electronic, electrical, photoelectric, luminescence, and photophysical properties [4 3 6].Previous studies revealed for the first time the high (without doping with dyes) intrinsic photoconductivity in the visible range of polyimides and polyquinazolones (integral photosensitivity 2 0 10 35 32.5 0 10 34 cm 2 J 31 ) whose polymeric chains contain in the diamine component of the repeating unit a quaternary carbon atom with various substituents or diamines of the heteroaromatic series [739]. The photoconductivity of the polyamides prepared from the same diamines ÄÄÄÄÄÄÄÄÄÄÄÄ is lower by two orders of magnitude [10].The photoelectric properties of films are associated with the excitation of the electronic systems of these polymers. It is known that the major factor governing the photoelectric properties of polyimide films is the donor3acceptor (DA) interaction in the polymer molecule. The character and intensity of this interaction depend on the structure of the repeating monomeric unit, packing of the macrochains, and surrounding of the arising complexes in the solid polyimide [6]. Polyimide macromolecules can be considered as DA chains of the alternating structure [11] in which the diimide fragment is the electron acceptor (A) and the diamine residue, the electron donor (D). With strong A (high electron affinity) and D (low ionization potential), the charge transfer is realized even in the ground (S 0 ) state, with the formation of intrachain complex 1 [Scheme 1, Eq. (1a)] and interchain complex 2 [Scheme 1, Eq. (1b)]. Scheme 1.AD~4 7 76 hn a~A 3 D +~7 6 hn f~( A 3 D + ) *~76~A D~, AD~7 6~A 3 DÃ D~4 7~A D +9 9 9 9 7 7 7 7 76 hn a~A 3 * DÃ D +9 9 9 9 7 7 7 7 76 hn f~A DÃ D~. (1a) (1b)
ÄÄÄÄÄÄÄÄÄÄÄÄSimultaneously, along with the overall absorption of D and A, a new long-wave band or shoulder appears in the electronic absorption spectrum, and the polymer films become colored [12]; also, a broad structureless fluorescence band appears. Its excitation spectrum reproduces the shape of the new absorption
